In article <2gf26k$7kv at mserv1.dl.ac.uk>, sdaviss at cosy.ab.umd.edu (Steven
Roy Daviss) wrote:
> At our journal club on Monday, while discussing an article which used
> response time as a dependent measure, the question was raised:
>> Is anything known about the neural circuitry involved in the
> estimation or perception of time?
Probably not what you want, but since I've been spending most of my time
lately working on response timing, I'll mention a few things.
It's a bit vague what you mean by perception of time. As far as temporal
processing goes, what I like to stress is that both stimuli and responses
are extended in time, and we need to consider these durations and not get
fooled into trying to analyze the problem as if moments in time were
accessible.
On the other hand, some of the best work that's been done on temporal
processing is from models where very small timing changes exist, as in
echo-locating bats. Catherine Carr wrote a review for Annual Review of
Neuroscience 16:223-243 (1993) on these systems.
But for longer time scales (that is beyond the microsecond-millisecond
range that applies to some special auditory systems) one of the key
insights seems to be that inhibition is important in producing changes in
timing. The best example of this as far as I'm concerned from my
chauvinistic perspective is the system I work on, namely the
geniculostriate pathway in cats. Lagged cells in the cat LGN transform
their retinal input through feedforward inhibition in order to obtain a
quarter-cycle delay relative to the retinal input or their neighboring
nonlagged cells. The complete range of response timings that gets sent to
cortex enables cortical cells to generate their fantastic response
specificities.
In this system we're talking about time scales on the range of hundreds of
milliseconds. You probably want to know about seconds, minutes, and hours.
I'll stop before I say something too ignorant about that, except to mention
a cute observation that was pointed out to me several years ago, and which
I didn't initially believe. It turns out that our perception of melody goes
away when the individual notes have durations of about 1 second. So my
sense of how we might process long time scales is that it's pretty obscure.
--
Alan Saul
saul+ at pitt.edu
